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Dear all,</div>
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We were trying to update the petsc version we use in our code to the version 3.19.1 when we noticed that some of the unit tests in our code started failing. The reason for the failure seems to be due to a change in the linesearch logic of petsc version 3.19.1.
In particular, the implementation of the function SNESLineSearchGetTolerances was modified such that maxstep is now scaled with fnorm as shown in the following link <a href="https://gitlab.com/petsc/petsc/-/blob/main/src/snes/linesearch/interface/linesearch.c#L1097" id="LPNoLPOWALinkPreview_3">https://gitlab.com/petsc/petsc/-/blob/main/src/snes/linesearch/interface/linesearch.c#L1097</a></div>
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<span style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">This change seems to be inconsistent with the way maxstep is being used later on to compute a step size using the l2 line search algorithm, for instance,
check the following code </span><a href="https://gitlab.com/petsc/petsc/-/blob/main/src/snes/linesearch/impls/l2/linesearchl2.c#L119" id="LPNoLPOWALinkPreview_1" style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt;">https://gitlab.com/petsc/petsc/-/blob/main/src/snes/linesearch/impls/l2/linesearchl2.c#L119</a><span style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);"> where
maxstep is compared to lambda_update and where maxstep is scaled by fnorm whereas lambda_update seems to be a scalar of a different order as computed here </span><a href="https://gitlab.com/petsc/petsc/-/blob/main/src/snes/linesearch/impls/l2/linesearchl2.c#L111" id="LPNoLPOWALinkPreview_2" style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt;">https://gitlab.com/petsc/petsc/-/blob/main/src/snes/linesearch/impls/l2/linesearchl2.c#L111</a><span style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);"> .</span><br>
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The way this change is reflected in our code is that we were trying to enforce a range for the step size provided by the l2 line search between 0.1 and 1 and now with the new changes in petsc version 3.19.1 the upper limit seems not to hold anymore and we are
seeing step sizes larger than 1.</div>
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Thank you in advance for your help.</div>
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Best regards,
<div>Nabil</div>
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